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Oscillating Seebeck coefficients in π-stacked molecular junctions.
Mohsin K Al-Khaykanee1,2, Ali K Ismael1,3, Iain Grace1
1Department of Physics, University of Lancaster Lancaster LA1 4YB UK c.lambert@lancaster.ac.uk mohsin.kad@gmail.com.
RSC Advances
|May 11, 2022
Summary
Molecular junctions exhibit tunable thermoelectric properties via pi-pi stacking. Quantum interference in para-connected molecules leads to bi-thermoelectric behavior, while meta-connected molecules offer stable performance.
Area of Science:
- Molecular electronics
- Nanoscale thermoelectricity
- Quantum interference phenomena
Background:
- Molecular junctions enable electron transport through pi-pi stacking between aromatic molecules.
- Thermoelectric properties of molecular junctions are crucial for energy harvesting and cooling applications.
- Oligo-phenylene ethynylene (OPE3) molecules serve as a model system for studying charge transport.
Purpose of the Study:
- Investigate the thermoelectric properties of molecular junctions formed by pi-pi stacking.
- Explore the influence of molecular structure and electrode connectivity on thermoelectric behavior.
- Understand the role of quantum interference in generating bi-thermoelectric effects.
Main Methods:
- Fabrication of molecular junctions using mono-thiol OPE3 molecules.
- Systematic variation of the pi-pi overlap length (L) in para-connected junctions.
- Measurement of Seebeck coefficients in both para- and meta-connected molecular junctions.
- Analysis of quantum interference effects using a molecular Mach-Zehnder interferometer model.
Main Results:
- Para-connected OPE3 junctions exhibit an oscillatory Seebeck coefficient as a function of pi-pi overlap length (L).
- Large positive and negative Seebeck coefficients (bi-thermoelectric behavior) were observed in para-connected junctions due to quantum interference.
- Meta-connected OPE3 junctions show a Seebeck coefficient that is insensitive to the overlap length (L).
- Control over electrode separation allows for tuning between hole-like and electron-like Seebeck coefficients in para-connected junctions.
Conclusions:
- Molecular junctions can be engineered to display tunable and switchable thermoelectric properties.
- Quantum interference is a key mechanism for achieving bi-thermoelectric effects in molecular systems.
- Meta-connected molecular junctions offer robust and predictable thermoelectric performance, suitable for resilient device design.
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